Rolling Bearing

ABSTRACT

A roller bearing for at least one set of roller bodies, which are disposed in an annular manner, the roller bearing having at least one track element with a track, on which the roller bodies are provided for rolling, includes the following features:—The track comprises a track base having a circular circumferential line,—the track element comprises, on each axial side of the track base, a shoulder or a rim for the roller bodies, each shoulder or rim having a circular circumferential line, and—the track element is formed such that, as viewed perpendicular to the planes defined by the circumferential lines, all center points of the three circumferential lines are different from each other.

The invention relates to a roller bearing for at least one set of roller bodies, which are disposed in an annular manner, the roller bearing having at least one track element with a track, on which the roller bodies are provided to roll.

For example, a ball bearing assembly for a wobble gearing is known from DE 34 00 679 A1, in which a so-to-speak normal grooved ball bearing is utilized, wherein only the bore of the bearing inner ring is formed in an inclined manner relative to an outer surface of the ball bearing inner ring.

An object of the present invention is to provide an improved roller bearing as compared to that.

The object is achieved by the subject matter of patent claim 1. Advantageous embodiments are described in the dependent claims.

According to claim 1, a roller bearing for at least one set of roller bodies, which are disposed in an annular manner, the roller bearing having at least one track element with a track, on which the roller bodies are provided for rolling, includes the following features:

-   -   The track comprises a track base having a circular         circumferential line,     -   the track element comprises, on each axial side of the track         base, a shoulder or a rim for the roller bodies, each shoulder         or rim having a circular circumferential line, and     -   the track element is formed such that, as viewed perpendicular         to the planes defined by the circumferential lines, all center         points of the three circumferential lines are different from         each other.

The invention is based on the recognition that, in a ball bearing arrangement according to the above-described DE 34 00 679 A1 for the typical case of a wobble gear, wherein a force is to be transferred in the axial direction, in particular, at one circumferential point of the outer ring of the ball bearing arrangement, the design of the two track elements with a track base and shoulders being concentric to each other is suboptimal, because the application of force on the shoulder portions, in particular, is quite variable depending on the rotational position of the ball bearing arrangement, with reference to said force transfer point. According to the invention, this is now overcome in that the track element is designed such that all center points of the three circumferential lines are different from each other, as viewed perpendicular to the planes defined by the circumferential lines of the track base and the shoulders and/or the rim, i.e., the circumferential lines are, so to speak, eccentric to each other. With the present invention, not only slightly-improved, but significantly longer lifetimes of the roller bearing can be achieved for comparable installation space utilization and comparable load situations like in the state of the art, which amounts to a quantum leap in the roller bearing field.

Further advantages, features and details of the invention result from the exemplary embodiment of the invention described in the following with the assistance of the FIGURE.

As an exemplary embodiment of the invention, the FIGURE shows a longitudinal section through a roller bearing according to the invention. The roller bearing comprises an inner track element 10 and an outer track element 20, between which are disposed a set of roller bodies that are formed as balls 30 and are disposed in an annular manner, wherein the balls 30 can be disposed in a not-illustrated cage. The inner track element 10 is formed such that, in one rotation of the inner track element about the rotational axis 5, the plane defined by a circumferential line of a track base 15 for the balls 30 performs a rocking motion about said rotational axis 5.

This rocking motion is correspondingly transferred to the outer track element 20. A pin 28 is disposed at a circumferential point on the outer surface of the outer track element 20 by friction welding, with which the reciprocation of the pin 28 in the direction of the rotational axis 5 caused by said rocking motion is transferred to another structural element, e.g., in the context of a hammer drill or a chisel hammer By friction welding the pin 28 onto the outer surface of the outer track element 20, expensive manufacturing methods, for example cutting out the pin 28, are advantageously avoided.

Both track elements 10 and 20 are formed with a track base 15 and 25 for the balls 30 and with shoulders 14 and 16 as well as 24 and 26 disposed on both sides of the track base 15 and 25. For each track element 10 and 20, the circular circumferential lines of the track base 15 and 25 as well as the two shoulders 14, 16 and 24, 26, respectively, all center points of the three circumferential lines are different from each other as viewed perpendicular to the parallel-to-each-other planes defined by the circumferential lines. As a result, in particular, the forces in the axial direction occurring during the rocking motion are absorbed and transferred by an always sufficiently-high dimensioned shoulder portion of the track elements 10 and 20.

In the FIGURE, a maximal inclination of the track base 15 of the inner track element 10 is illustrated. The two shoulders 14 and 16 of the inner track element 10 are formed such that their circumferential lines reach this maximal inclination earlier or later, e.g., by 10° in an advanced or lagging manner, wherein this depends on the particular operating conditions of the roller bearing. In other embodiments, the advancing or lagging can also be greater or less than 10° or the track elements can also be formed such that the track base and the shoulders reach said maximal inclination at the same time. It is important, however, that the force demand profile, which is predetermined by the installation environment and the intended usage, is dependent on the rotational position of the roller bearing.

The outer track element 20 is constructed in a manner corresponding to the inner. For the outer track element 20, the particulars of the advancing and lagging of the shoulders 24 and 26, which was previously described for the inner track element 10, can be described in a more simple manner in that the center points of the circumferential lines of both shoulders 24 and 26 lie offset relative to a straight line that extends through the center point of the circumferential line of the track base 25 of the outer track element 20 and the connection point of the pin 28.

In one embodiment, the track elements 10 and 20 are, in particular, made of a case-hardened steel having a relatively high nickel content. In other embodiments, the inner track element 10 can also be formed, e.g., in two pieces, in that the track base 15 and the shoulder 14 and 16 are formed similar to the outer track element 20 and it is then installed in an appropriate manner in a second piece.

Summarized in a catch phrase manner, one can also describe the above-described roller bearing as a three-point-optimized wobble bearing. 

1. A roller bearing for at least one set of roller bodies, which are disposed in an annular manner, the roller bearing having at least one track element with a track, on which the roller bodies are provided for rolling, including the following features: The track comprises a track base having a circular circumferential line, the track element comprises, on each axial side of the track base, a shoulder or a rim for the roller bodies, each shoulder or rim having a circular circumferential line, and the track element is formed such that, as viewed perpendicular to the planes defined by the circumferential lines, all center points of the three circumferential lines are different from each other.
 2. A roller bearing according to claim 1, wherein the track element is provided to rotate about a rotational axis that has an inclination relative to the planes so that the plane of the track base is provided for performing a rocking motion relative to the rotational axis.
 3. A roller bearing according to claim 2, wherein the rocking motion of the plane of the track base is characterized, when laterally viewing the rotational axis, by two end positions having maximal inclination relative to the rotational axis, and the track element is formed such that the end positions of the planes of the shoulders or rims are reached in an advanced or lagging manner by a predetermined angle as compared to the end positions of the plane of the track base.
 4. A roller bearing according to claim 3, wherein the end positions of the planes of the two shoulders or the rims are different from each other.
 5. A roller bearing according to claim 4, wherein the center points of the circumferential lines of both shoulders or rims are disposed in a point symmetric manner relative to a center point of the circumferential line of the track base.
 6. A roller bearing according to claim 5, wherein the roller bearing comprises at least two track elements, between which the roller bodies are disposed, and the track elements are formed in a manner corresponding to each other.
 7. A roller bearing according to claim 6, wherein at least one circumferential portion of one of the track elements is provided to transfer a force onto at least one additional structural element.
 8. A roller bearing according to claim 7, wherein the track element comprises an extension in said circumferential portion.
 9. A roller bearing according to claim 8, wherein the extension is attached by friction welding.
 10. A roller bearing according to claim 9, wherein the center points of the circumferential lines of both shoulders or rims lie offset relative to a straight line that extends through the center point of said circumferential portion and the center point of the circumferential line of the track base.
 11. A roller bearing according to claim 10, wherein the roller bodies are formed as balls.
 12. A roller bearing comprising: at least one track element including a track having a track base and first and second shoulders disposed on opposite sides of the track base as viewed in an axial direction of the roller bearing, the circumferences of the track base, first shoulder and second shoulder each being circular, the three respective circles defining three respective planes, and at least one set of roller bodies disposed in an annular manner around the track base, wherein the track base, first shoulder and second shoulder are configured such that, as viewed perpendicular to the planes defined by the respective circles, the center points of the three circles do not overlap.
 13. A roller bearing according to claim 12, wherein the track element is configured to rotate about a rotational axis that is oblique relative to the planes so that the plane of the track base performs a rocking motion relative to the rotational axis during each revolution of the track element.
 14. A roller bearing according to claim 13, wherein the rocking motion of the plane of the track base is bounded, when viewed laterally to the rotational axis, by two end positions having maximal inclination relative to the rotational axis, and the track element is formed such that the end positions of the planes of the shoulders are reached in an advanced or lagging manner by a predetermined angle as compared to the end positions of the plane of the track base.
 15. A roller bearing according to claim 14, wherein the respective end positions of the planes of the first and second shoulders are different from each other.
 16. A roller bearing according to claim 12, wherein the center points of the circles defined by the circumferences of the first and second shoulders are disposed in a point symmetric manner relative to the center point of the circle defined by circumference of the track base.
 17. A roller bearing according to claim 12, wherein the roller bearing comprises at least two track elements, between which the roller bodies are disposed, and the track elements are formed in a manner complementary to each other.
 18. A roller bearing according to claim 17, further comprising an extension projecting from a circumferential portion of one of the track elements, the extension being configured to transfer a reciprocating force to at least one additional structural element.
 19. A roller bearing according to claim 18, wherein the circles defined by the circumferences of the first and second shoulders lie offset relative to a straight line that extends through the center point of said circumferential portion and the center point of the circle defined by the circumference of the track base.
 20. A roller bearing according to claim 19, wherein the center points of the circles defined by the circumferences of the first and second shoulders are disposed in a point symmetric manner relative to the center point of the circle defined by circumference of the track base. 